Plant Industry - Emerald Ash BorerNew Jersey Department of Agriculture.Emerald Ash Borer was discovered in New Jersey in May 2014 in Somerset County, and as of August 2016 has also been found in Bergen, Burlington, Essex, Hunterdon, Mercer, Middlesex, and Monmouth counties. Infestations throughout the U.S. and Canada have killed tens of millions of ash trees since 2002. Report signs of the beetle to the Department of Agriculture at 609-406-6939.